Twisting motion and process for producing wire cords

ABSTRACT

This invention relates to twisting machine and process for producing wire cords particularly suitable for use in reinforcement of vehicle tires and other various articles of rubber or plastics. An over twister is provided between a rotating double twister adapted to twist together a plurality of wire elements, including pre-twisted wires, and a stationary take up means. The over twister consists of rollers turning about a path of travel of the twisted wire cord in the counter direction to the rotation of the double twister at a speed of revolution sufficient so as to convert at least part of the elastic strain in the wire elements which has been imparted by the double twister, to a corresponding permanent torsional strain, thereby improving the straightness of the finished wire cord and minimizing the tendency of the wire cord to become untwisted and curled as well as enabling higher speed production of twisted wire cords.

United States Patent [1 1 Taketomi et al.

[ Nov. 13, 1973 1 1 TWISTING MOTION AND PROCESS FOR PRODUCING WIRE CORDS[75] Inventors: Kameo Taketomi; Tomoaki Katsumata; Norihisa Matsushima;

Masaari Yoneji, all of ltami, Japan [73 I Assignee: Sumitomo ElectricIndustries, Ltd.,

Nigashi-ku, Osaka, Japan [22] Filed: Mar. 16, 1972 [21] Appl. No.:235,273 [30] Foreign Application Priority Data March 16, 1971 Japan..46/14103 [52] US. Cl 57/58.57, 57/5859, 57/166 [51] Int. Cl. D07b3/00, D07b 7/08, D02g 3/48 [58] Field of Search 57/58.3, 58.32, 58.49,57/58.52, 58.57, 58.59, 58.7, 58.72, 58.83,

Primary Examiner-Donald E. Watkins Attorney-Richard C. Sughrue et a1.

[57] ABSTRACT This invention relates to twisting machine and process forproducing wire cords particularly suitable for use in reinforcement ofvehicle tires and other various articles of rubber or plastics. An overtwister is provided between a rotating double twister adapted to twisttogether a plurality of wire elements, including pretwisted wires, and astationary take up means. The over twister consists of rollers turningabout a path of travel of the twisted wire cord in the counter directionto the rotation of the double twister at a speed of revolutionsufficient so as to convert at least part of the elastic strain in thewire elements which has been imparted by the double twister, to acorresponding permanent torsional strain, thereby improving thestraightness of the finished wire cord and minimizing the tendency ofthe wire cord to become untwisted and curled as well as enabling higherspeed production of twisted wire cords.

5 Claims, 5 Drawing Figures PATENTEDHUV 13 I975 3,771; 304' SHEET 10F 3FIG. I

PATENTED NEW 13 I975 SHEET 2 OF 3 FIG. 2

ELASTIC STRAIN wmmmkm 20 mmO.

NUMBER OF TWIST PER UNIT LENGTH IOOO ZOQO 3000 NUMBER 8F REVOLUTI N 5 5POSI- E POSITION 5 TION 8P l 2 POSITION B o FIG. 3

TWISTING RATIO OF OVER TWISTER PATENTEDHUV 13 I975 SHEET 3 OF 3 FIG. 4

TWISTING MOTION AND PROCESS FOR PRODUCING WIRE CORDS BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to a twistingmachine and process for producing wire cords particularly suitable foruse in reinforcement of vehicle tires and other articles of rubber orplastics.

2. Description of the Prior Art A double twister for producing electricconductors or similar materials is well known which includes supplyreels mounted on a frame for supplying a plurality of individual wireelements which are led through a rotating arcuate guide to form aballoon and thus imparted with a double twist per revolution of thearcuate guide and then taken up as a twisted wire cord on a take-upmeans provided on a floating cradle within the rotating arcuate guide.

However, when making steel cord and other high elasticity materials sucha double twister system results in a significant amount of residualtorsional stress in the twisted wire cord which tends to untwist or curlwhen unrestrained.

To eliminate this problem, it would be possible to opcrate the doubletwister at a considerably higher speed than that required for impartingthe desired amount of actual twist to the wire elements so that anadditional amount of twist corresponding to the elastic strain isimparted to the wire elements and then the excess twist is diminished ator after the taking-up stage of the finished wire cord by any kind ofuntwisting method.

Such higher speed rotation and untwisting action can lead to aconsiderable reduction in useful life of the bearings and otherstructural elements used in the double twister and the possibility ofthe wire cord breaking will be increased.

SUMMARY OF THE INVENTION It is a primary object of the present inventionto provide a new and improved twisting machine for producing wire cordswhich overcomes the above-mentioned problems and wherein the residualelastic strain in the finished wire cord is effectively controlled andreduced without need for exceptionally high speed rotation of the doubletwister.

In one aspect of the invention, there is provided a wire twistingmachine which comprises an over twister including rollers disposedbetween a double twister rotating about a floating cradle to form aballoon of a plurality of wire elements including pre-twisted wires,drawn from the supply reels, and a stationary take-up means, saidrollers being adapted to turn in a direction counter to the rotation ofthe double twister about a path of travel of the twisted wire cordpassing through the machine at a speed of revolution sufficient toconvert at least part of the elastic strain which has been imparted tothe wire cord by the double twister, to a corresponding permanenttorsional strain.

The above and other objects, features and advantages of the inventionwill become apparent by the following description taken in conjunctionwith the accompanying drawings wherein one practical form of the presentinvention is shown only by way of example and not limitation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing apreferred embodiment of the twisting machine for producing wire cords inaccordance with the invention;

FIG. 2 is a diagram showing the torsion stress imposed to the wire cord31 by the machine of FIG. 1;

FIG. 3 is a diagram showing the relation between the twisting ratio ofthe over twister used in the twisting machine of the invention and thenumber of residual twists per unit length of the finished wire cord;

FIG. 4 is a side elevational view showing the wire tension adjustingdevice incorporated upon each of the individual supply reels 6 used inthe twisting machine of FIG. 1; and

FIG. 5 is a perspective view of the break detector means used in thetwisting machine of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, andparticularly to FIG. 1, the twisting machine of the invention includesan over twister 4 provided between a double twister 1 and a take-upmeans 2, the over twister consisting of rollers 41 adapted to turn in adifferent direction to the rotation of the double twister 1 about thepath of travel of the twisted wire cord 31 at a speed of revolutionsufficient to convert the elastic strain imposed on the individual wireelements 3 forming the wire cord 31 by the double twister 1 to acorresponding permanent strain.

As shown in FIG. 1, the double twister 1 includes a plurality of supplyreels 6 supported by a floating cradle 5. Each of the supply reels 6incorporates a wire tension adjusting device having a configuration tobe described later with reference to FIG. 4.

The double twister further includes a pair of spaced rotary disc frames8a and 8b rotated at the same speed of revolution by a common drivemotor 7. The twisted wire cord 31 is led from one of the rotating frames8a to the other rotating frame 8b with or without assistance of arotating arcuate guide member 15 which rotates around the floatingcradle 5 is such a manner that the core 31 forms a balloon between therotating frames 8a and 8b.

The floating cradle 5 is supported by stub shafts 13a and 13b joumaledin ball bearings 14a and 14b within the rotating frames 8a and 8b. Thus,the floating cradle 5 will remain stationary even when the frames 8a and8b rotate.

The individual metallic wire elements 3 drawn from the supply reels arepassed separately through the holes of a lay plate 9 and into theopening of a die 10 in which the individual wire elements are gatheredto form a single compact bundle.

While the individual wire elements are drawn separately from therespective supply reels 6 in the illustrated embodiment, it should beunderstood that a number of individual wire elements 3 may be drawn froma single supply reel.

The over twister 4 which consists of the rollers 41 rotating about thepath of travel of the twisted wire cord 31 in the counter direction tothe rotation of the rotating frames 8a and 8b of the double twister l islocated downstream of the double twister 1. The rotational speed of theover twister 4 is controlled to impart to the twisted wire cord 31 anamount of additional twist sufficient to partially or wholly convert theelastic strain which has been imparted to the individual wire elements 3by the double twister 1, to a corresponding permanent strain so that thefinished wire cord 31 coiled on the take-up means will have no elasticstrain (residual torsion stress).

A speed controller 11 is incorporated in the drive means of the overtwister 4 for altering the speed of rotation of the over twister becausethe amount of elastic strain present in the wire elements varysdepending upon the diameter, strength and tension of the individual wireelements 3 comprising the twisted wire cord 31.

It is believed, however, that the speed controller 11 may be omitted insituations where it is desired to twist wire elements having identicalsize and properties at all times.

The two rollers 41 of the over twister 4 are mounted in staggeredrelation on the opposite sides of the effective path of travel of thetwisted wire cord so that the twisted wire cord 31 is passed over theserollers 41 to a figure eight pattern.

As will be understood by those skilled in the art, other over twisterconfigurations providing a similar result may be employed instead of thepresent two roller arrangement. For example, only a single roller 41could be employed.

A take-up capstan 12 is provided between the over twister 4 and thetake-up reel 2 for advancing the twisted wire cord. During the travelfrom the over twister to the take-up reel 2, the elastic strain presentin the individual wire elements of the wire cord 31 is relieved byvirtue of the excess counter twist imparted by the over twister and thefinished wire cord is coiled on the take-up reel 2 without any elasticstrain or in otherwise good-controlled condition.

Automatic operation of the speed controller of the over twister may beprovided by the use of a torsion senser roll (not shown) located betweenthe capstan l3 and the take-up reel 2 for detecting the amount of thetorsion stress remaining in the wire cord 31.

Referring now to FIG. 5, there is shown detailed configuration of abreak detector means 16 which is located between the two take-up rolls12 over which the wire cord runs in parallel side-by-side loops orturns. As shown in this figure, the break detector means comprises aU-shaped insulating member having an open end and which extends acrossthe full width of the parallel loop web of the twisted wire cord. Theinner surface of the U-shaped insulating member is entirely covered byan electric conductive plate 18, such as a copper plate, so that asufficient clearance between the wire cord loops and the electricconductive plate 18 is maintained during normal operating conditions.

Upon the occurrence of a break in the twisted wire cord 31 the end ofthe broken wire element springs out beyond the outer surface of thetwisted wire cord 31 so that it will contact with the electricconductive plate 18 as the portion of the wire cord having the breakpasses through the break detector means 16. Any break in the individualwire elements of the wire cord is thus electrically detected in an easyand reliable manner.

It may be preferable that the break detector means is operably connectedto the drive means of the twisting machine in order to automaticallystop the machine operation upon the detection of a break.

Since the wire elements used to form certain types of wire cords, suchas steel cords, are generally extremely thin and small in diameter withlittle lengthwise elongation capability, the breaking or tearing of theindividual wire elements occurs frequently during high speed operationof the twisting machine and cannot be easily detected, particularlyafter the wire elements have been twisted together.

In accordance with the invention, however, accurate and reliabledetection of any break in the individual wire elements is achieved bythe above break detector means which extends over a plurality of spacedpoints of the twisted wire cord running in side-by-side loops.

Such accurate and reliable break detection results in substantialmaterial saving and more efficient and increased out put production.

Assuming that the double twister l is rotating at 1,500 rpm. and anumber of individual wire elements are drawn from the supply reels 6through the respective holes of the lay plate 9 and through the openingof the die 10 as a single bundle and then passed in the form of aballoon between the frames 8a and 8b rotated by the drive motor 7, thebundle of individual wire elements is twisted by the 1,500 rpm. rotationof the rotating frame 8a and thereafter additionally twisted by the1,500 rpm. rotation of the rotating frame 8b. The total amount oftwisting imparted to the wire elements by the two rotating frames isthat of 3,000 rpm. rotation.

If the wire cord were directly taken up by the take-up reel, thefinished wire cord would contain substantial elastic strain whichcreates a tendency for the finished wire cord to spring back and becomeuntwisted and curled even when the wire cord is rewound is such a manneras to remove the elastic strain, whereupon the finished wire cord doesnot have the desired amount of twist.

By contrast, in accordance with the invention, the elastic strain, suchas that corresponding to a 1,000 r.p.m. speed of revolution, in theindividual wire elements of the twisted wire cord 3 can be partially orwholly removed by the over twister 4 which is rotated in a directioncounter to the revolution of the double twister 1 at 1,000 rpm. Thetotal amount of twist imparted to the wire cord by the double twister land the over twister 4 is that of a 4,000 rpm. speed of rotation but thetwisted wire cord is untwisted by the residual elastic straincorresponding to a 1,000 rpm. speed of revolution as it passes from theover twister 4 to the take-up capstan 12 so that a finished wire cordprovided with twist exactly corresponding to a 3,000 rpm. speed ofrotation will be taken up on the take-up reel without any residualtorsion stress.

FIG. 2 is a diagram showing the relation between the torsion stressimparted to the wire cord passing from the supply reels 6 to the take-upreel 2 and the twisting number per unit length of the twisted wire cord.

Example: I

Four steel wire elements (AISI C1070, tensile strength 285 kg/mm) weretwisted together with a twisting pitch of 9.5 mm to form a twisted cord.FIG. 3 shows the relation between the twisting ratio of the over twisterand the twisting number per unit length of the twisted wire cord.

The twisting ratio R in the over twister is defined by:

R percent (B/2A B) X 100 wherein A is the rotational speed of the doubletwister in r.p.m.

The residual twisting number is determined by the number of twistsremaining in each 1 M of the twisted wire cord taken up on the reel andalgebraic signs and designate the directions of the twists.

While the optimum twisting ratio of the over twister depends upon thesize, strength, strand lay length, quality of the wire elements used andthe amount of twist in the double twister as well as the nature ofsubsequent treatment processes to take place on the wire cord, atwisting ratio less than 60 percent, preferably of to percent, has beenfound from various tests to be satisfactory.

The torsion stress in the individual wire elements of the twisted wirecords is also influenced by the characteristics of the wire elements andby non-uniformity in tension of the individual wire elements as they aredrawn from the supply reels. The non-uniform tension leads tonon-uniformity in wire twisting effect which adversely affects thestraightness of the twisted wire cord. Moreover, the non-uniform tensionwould sometimes result in breaks in the individual wire elements beingtwisted.

In order to eliminate this problem, a tension adjusting device isincorporated upon each of the supply reels 6, having a configurationshown in FIG. 4. In this figure, the supply reel 6 with a winding of themetallic wire element 3 is mounted within the floating cradle 5 by meansof a reel shaft 19.

A braking wheel 20, which has an annular groove for receiving a tensionbelt,or rope, 21 extending around the braking wheel, is fixedlyconnected to one of the end flanges of the supply reel 6 for rotationwith the supply reel 6 on the reel shaft 19. Urged and maintained insliding contact with the outermost layer 30 of the winding of wireelement 3 is a friction roller 29 which is supported by an arm 22pivoted at the other end 34 on the floating cradle.

A coil spring 24 has one end pivotally connected to the arm 22 at 28 andthe other end connected to one arm 27 of an L-shaped member 23 which ispivotally mounted on the floating cradle at 32. The effective length ofthe coils spring can be varied and adjusted by adjustable lock nutsengaging on a threaded rod 33.

The other arm 26 of the L-shaped member is connected to a free end of atension belt 21 extending around and engaging in a portion of theannular groove of the braking wheel 20 and fixedly connected to thefloating cradle at the other end 25.

It should be noted that the pivots 25, 34 and 32 are located within thefloating cradle radially outward of the supply reel 6.

With the wire tension adjusting device above described, as the diameterand quantity of the winding 30 of wire element 3 on the supply reel 6decrease because of withdrawal and supply of the wire element 3 to thetwister, the arm 22 is allowed to turn in the direction of the arrow inFIG. 4 so that the pulling force exerted to the tension belt 21 by thelinkage including the arm 22, the spring 24 and the L-shaped member 23is correspondingly diminished, thereby avoiding an increase of tensionin the wire element with the decrease in diameter of the winding on thesupply reel so as to maintain a substantially uniform tension in thewire element drawn from the reel. Thus, the wire tension adjustingdevice facilitates uniform and constant twisting effect and,accordingly, improves the straightness of the finished wire cord as wellas avoiding breakage during the twisting process.

From the foregoing, it should be readily understood that the amount ofpermanent twist in the finished wire cord can be readily varied andcontrolled by untwisting at least part of the elastic strain imparted tothe wire cord by the double twister, using the over twister 4 whichimparts a certain amount of torsion stress in the counter direction tothe twisting action of the double twister whereby the wire cord will beuntwisted to remove or reduce the residual elastic strain before thewire cord is coiled on the take-up reel 2.

The finished wire cord is a twisted wire element combination resultingfrom elastic torsional stress imparted thereto and, accordingly, isrelatively free of curl or distorsion, providing improved straightnesscapability as well as minimizing the possibility of the cord endbecoming loose and untwisted.

It should also be noted that the arrangement of the over twister 4 inseries with the double twister 1 facilitates a more simplified andaccurate control of the amount of permanent torsional stress present inthe final wire elements than if a large maount of twist corresponding tothe total twist by the double twister l and the over twister 4 isachieved by a single twister unit. Since exceptionally high speedrotation is not required, the equipment can be greatly simplified andexhibit a long extended usage.

Further, the twisting machine of the invention will be readily adaptedfor combining the wire twisting process with the subsequent overtwisting and wrapping steps to provide a tandem manufacturing system.

What is claimed is:

l. A wire twisting machine comprising a double twister having at leastone supply reel in a floating cradle for imparting twist to a pluralityof individual wire elements drawn from said supply reel, a stationarytake-up means, and an over twister provided between said double twisterand said take-up means, said over twister including roller elementsadapted to turn about the path of travel of a twisted wire cord in adirection counter to the rotation of said double twister and at a speedof revolution sufficient to convert at least part of the elastic strainwhich has been imparted to the individual wire elements by said .doubletwister to a corresponding permanent strain.

2. A wire twisting machine defined in claim 1 wherein said over twisterincludes two spaced rollers adapted to turn about the effective path oftravel of the wire cord, said rollers being arranged so that a portionof the wire cord extends around said two spaced rollers in a figureeight.

3. A wire twisting machine defined in claim 1 which further includes awire tension adjusting device comprising a braking wheel rigidly mountedon each supply reel, a tension belt secured to said cradle at one endand extending around said braking wheel, an arm pivoted at one end tosaid cradle and slidably engaging the outermost layer of a wire windingon the supply reel by means of the other end thereof, and linkage meanssecured to the other end of said belt and said arm to vary the forceapplied to said tension belt on said braking wheel in dependence uponthe angular displacement of said arm with a decrease in the diameter ofthe winding on the supply reel.

4. A wire twisting machine defined in claim 1 which further includescapstan means, break detector means said floating cradle, imparting overtwist to the twisted wire cord by roller means turning about the path oftravel of the wire cord in a direction counter to that of said doubletwisting and at a speed of revolution sufficient to convert at leastpart of the elastic strain which has been imparted to said individualwire elements in the previous double twisting step to a correspondingpermanent strain, and taking up the twisted wire cord.

1. A wire twisting machine comprising a double twister having at leastone supply reel in a floating cradle for imparting twist to a pluralityof individual wire elements drawn from said supply reel, a stationarytake-up means, and an over twister provided between said double twisterand said take-up means, said over twister including roller elementsadapted to turn about the path of travel of a twisted wire cord in adirection counter to the rotation of said double twister and at a speedof revolution sufficient to convert at least part of the elastic strainwhich has been imparted to the individual wire elements by said doubletwister to a corresponding permanent strain.
 2. A wire twisting machinedefined in claim 1 wherein said over twister includes two spaced rollersadapted to turn about the effective path of travel of the wire cord,said rollers being arranged so that a portion of the wire cord extendsaround said two spaced rollers in a figure eight.
 3. A wire twistingmachine defined in claim 1 which further includes a wire tensionadjusting device comprising a braking wheel rigidly mounted on eachsupply reel, a tension belt secured to said cradle at one end andextending around said braking wheel, an arm pivoted at one end to saidcradle and slidably engaging the outermost layer of a wire winding onthe supply reel by means of the other end thereof, and linkage meanssecured to the other end of said belt and said arm to vary the forceapplied to said tension belt on said braking wheel in dependence uponthe angular displacement of said arm with a decrease in the diameter ofthe winding on the supply reel.
 4. A wire twisting machine defined inclaim 1 which further includes capstan means, break detector meansdisposed to extend across a plurality of parallel loops of a twistedwire cord running over said capstan means, said break detector meanscomprising a U-shaped insulating member including an open end and havingthe inner surface thereof covered by an electrically conductive plate.5. A process of producing wire cord, comprising the steps of impartingdouble twist to a plurality of individual wire elements drawn from atleast one supply reel within a floating cradle and forming a balloonaround said floating cradle, imparting over twist to the twisted wirecord by roller means turning about the path of travel of the wire cordin a direction counter to that of said double twisting and at a speed ofrevolution sufficient to convert at least part of the elastic strainwhich has been imparted to said individual wire elements in the previousdouble twisting step to a corresponding permanent strain, and taking upthe twisted wire cord.